Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/22—After-treatment of expandable particles; Forming foamed products
  • C08J9/224—Surface treatment
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2325/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Derivatives of such polymers
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
  • Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]
  • Y10T428/2991—Coated
  • Y10T428/2998—Coated including synthetic resin or polymer

Definitions

• This invention relates to a process for making expandable styrene polymer particles non-lumping on pre-expansion.
• the particles are generally pre-expanded before introduction into the mold to provide better fusion and less density variation in the molded article.
• Such a pre-expansion is described in U.S. Pat. No. 3,023,175 and 3,577,360.
• pre-expanded particles are placed into a mold cavity which defines the shape of the desired finished articles.
• the particles are heated above their softening point, whereupon the particles expand to fill the mold cavity and fuse together.
• anti-lumping, pre-expanded particles have density of less than 0.90 pcf. are produced by coating styrene polymer particles with a calcium polysilicate applied to the particles by dry-blending techniques or an aqueous suspension after impregnating the particles with expanding agent.
• the suitable polysilicate analyzes as 73-83 weight % SiO 2 , 3-7 weight % CaO, less than 1 weight % Al 2 O 3 and the remainder as water.
• the polymers may be derived from vinyl aromatic monomers including styrene, vinyltoluene, isopropylstyrene, alpha-methylstyrene, nuclear methylstyrenes, chlorostyrene, tert-butylstyrene, etc., as well as copolymers prepared by the copolymerization of a vinyl aromatic monomer with monomers such as butadiene, alkyl methacrylates, alkyl acrylates, acrylonitrile and maleic anhydride wherein the vinyl aromatic monomer is present in at least 50% by weight of the copolymer.
• these polymers and copolymers are referred to herein as styrene polymers.
• the styrene polymers can, of course, be produced by any of the known techniques, for example by suspension or mass polymerization, to obtain particles in the form of beads or pellets.
• the blowing agent is incorporated into the particles, as in U.S. Pat. No. 2,983,692, by suspending the particles in water with the aid of suspending agent systems such as tricalcium phosphate in combination with an anionic surfactant.
• blowing agents are compounds which are gases or which will produce gases on heating.
• Preferred blowing agents include aliphatic hydrocarbons containing from 4-7 carbon atoms in the molecule, such as butane, pentane, cyclopentane, hexane, heptane, cyclohexane, and the halogenated hydrocarbons which boil at a temperature below the softening point of the polymer. Mixtures of these agents may also be used, such as a mixture of 40-60% n-pentane and 60-40% trichlorofluoromethane. Usually from 3 to 20% of blowing agent per 100 parts of polymers is incorporated by the impregnation.
• the impregnation is conventionally carried out at temperatures ranging from about 60° to 150° C. Increasing the temperature makes the impregnation proceed at a faster rate.
• the suspension of polymer particles is cooled to room temperatures to allow separation of the impregnated beads from the aqueous phase.
• the hydrated calcium polysilicate useful in this invention is a finely divided powder consisting of 73-83 weight % of silicon dioxide, 3-7 weight % of calcium oxide, less than 1 weight % of aluminum oxide, and the remaining 9-20 weight % being water.
• the polysilicate is useful in amounts of from 0.02 to 0.05 part per 100 parts of polymer particles (0.02-0.05 weight % based on polymer weight).
• the expandable styrene polymer particles can be coated with the hydrated calcium polysilicate in any convenient manner, for example, by dry blending the polymer particles with the polysilicate in conventional dry blending equipment.
• the polysilicate can be added to the aqueous suspension of expandable polymer particles in which the particles were initially prepared.
• the dried polymer particles from any type of polymerization can be suspended in aqueous medium to be impregnated with blowing agent, and the polysilicate added to this suspension slurry after impregnation but prior to separation of the impregnated particles.
• the coated, impregnated particles are separated from the aqueous phase by the usual means, such as filtration a careful manner so as not to remove the coating from the beads.
• the particles are then dried in air.
• coating process of the present invention may also be applied to polymer particles which contain various other additives, such as dyes, pigments, self-extinguishing agents, anti-static agents, plasticizers or the like.
• Expandable polystyrene beads were prepared by adding to a reactor equipped with a three-bladed impeller in the following order, with stirring 100 parts of styrene, 0.33 part of a catalyst (consisting of 0.23 part of benzoyl peroxide and 0.10 part of t-butyl perbenzoate), 108 parts of water, 0.05 part of a buffer tetrasodium pyrophosphate, and the reactor was heated to 92° C. over 1.5 hours. Then, 0.150 part of a suspending agent, hydroxyethyl cellulose, was added and the mixture maintained at 92° C. for an additional 3.5 hours.
• a dispersing agent Tween 20 (polyoxyethylene sorbitan monolaurate) and over a period of 1.5 hours 8.5 parts of the blowing agent, n-pentane, were added.
• the temperature of the suspension was then raised to 115° C. over a period of 0.5 hour and maintained at 115° C. for an additional 4 hours to complete the polymerization of the monomer and the impregnation of the blowing agent into the particles.
• the slurry was divided into aliquots A and B.
• Example I Aliquot A of Example I was divided into five portions. One portion Al was set aside. To the second portion A2 there was added 0.02 part per 100 parts of polymer of the anti-lumping agent of U.S. Pat. No. 3,444,104, amorphous hydrated calcium silico aluminate (50% SiO 2 , 67% Al 2 O 3 , 30% CaO, 13% H 2 O), and the slurry was stirred with a three-bladed impellor for 15 minutes to thoroughly coat the particles with the anti-lumping agent. The particles were then dewatered, and air dried.
• amorphous hydrated calcium silico aluminate 50% SiO 2 , 67% Al 2 O 3 , 30% CaO, 13% H 2 O
• A3 there are added 0.04 part per 100 parts of polymer of the same aluminate, anti-lumping agent and the slurry was stirred for 15 minutes after which the particles were dewatered, and air dried.
• 0.02 part per 100 parts of polymer of the anti-lumping agent of the present invention i.e., a hydrated calcium polysilicate (83% SiO 2 , ⁇ 1% Al 2 O 3 , 7% CaO, >9% H 2 O), and the slurry was stirred for 15 minutes after which the particles were dewatered, and air dried.
• each portion A1 through A5 was separately pre-expanded in a Rodman pre-expander as described in U.S. Pat. No. 3,023,175 using in each case a steam pressure of 20 psig and feed rate of 200 lbs./hr.
• the pre-expanded beads having a bulk density of 1.5 lbs./cu. ft. were recovered from the bead hopper, were allowed to air dry in paper containers for approximately 18 hours, and then were screened through a No. 31/2 mesh U.S. Standard Sieve.
• the percent lumping was determined from the weight of the beads which were retained on the screen.
• Portion A1 the beads containing no anti-lumping agent, had 3 percent by weight of lumps.
• Example II The amount of lumps as determined by the procedure of Example II is recorded in Table I.
• the portions of the pre-expanded beads were placed in individual 5 ⁇ 5 ⁇ 3/8 inch molds and the molds placed between the platens of a conduction press at a temperature of 250° F. where the beads were heated to expand them and cause them to fuse together. Fusion was good in all cases.
• the coated polymer beads were placed in a 25 gallon cylindrical horizontal ribbon blender designed for vacuum and jacketed for steam heating. One pound samples of the coated polymer beads were placed in the blender for the times indicated in Table II at 240° F. and subjected to a vacuum equal to 25 inches of mercury, then the vacuum vented during a 10 second period followed by bead discharge. The percent lumps were determined by screening, where possible, as in Example II. Sample 1 contained no additive. Samples 2 and 3 contained the calcium silico aluminate in concentrations of 0.02 and 0.04 weight % based on polymer respectively. Samples 4 and 5 contained the calcium polysilicate in 0.02 and 0.04 weight % concentration, respectively.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)

Priority Applications (11)

Applications Claiming Priority (1)

Publications (1)

Family

ID=24584538

Family Applications (1)

Country Status (11)

Cited By (6)

Families Citing this family (3)

Citations (3)

Family Cites Families (9)

• 1975
  • 1975-12-29 US US05/644,355 patent/US4029613A/en not_active Expired - Lifetime
• 1976
  • 1976-08-10 CA CA258,773A patent/CA1053400A/en not_active Expired
  • 1976-08-26 JP JP51102149A patent/JPS598294B2/ja not_active Expired
  • 1976-09-30 SE SE7610837A patent/SE408650B/xx not_active IP Right Cessation
  • 1976-10-05 FI FI762821A patent/FI63048C/fi not_active IP Right Cessation
  • 1976-10-06 IT IT51599/76A patent/IT1069280B/it active
  • 1976-10-07 NL NL7611079A patent/NL7611079A/xx not_active Application Discontinuation
  • 1976-12-21 GB GB53289/76A patent/GB1561887A/en not_active Expired
  • 1976-12-22 FR FR7638710A patent/FR2337168A1/fr active Pending
  • 1976-12-28 BE BE173703A patent/BE849931A/xx unknown
  • 1976-12-29 DE DE2659403A patent/DE2659403C2/de not_active Expired

Patent Citations (3)

Also Published As

Similar Documents

Legal Events